This used to happen to me all the time on my old netbook. Often times for a whole minute I couldn't navigate the page because of a flash ad. I used both chrome and firefox and it happened consistently. No problems with my new one anymore though...don't know why that happened since they're both practically the same netbook.

I find the best thing to do any time a browser is giving you trouble is the following things:

1) Make sure you have the latest version.

2) Clear your history of everything. In FireFox you do that by...

Tools > Clear Recent Search History... (Then check all the boxes and then click 'Clear Now'. Or, if you don't want to delete everything, at least make sure to check 'cache' and 'cookies' and 'site preferences'.).